A population-based case-control study to examine the effects of occupational exposures on the subsequent risk of prostate cancer is proposed. Cases of prostate cancer (N approx. 1,500) who are; 1) 50 to 74 years of age at diagnosis, 2) newly diagnosed during a two year period, 3) resident in Wayne County (which includes the city of Detroit) at the time of diagnosis, 4) living at the time of identification, and 5) in possession of a telephone at the time of diagnosis, will be identified through the Metropolitan Detroit Cancer Surveillance System (a participant in the Surveillance, Epidemiology, and End Results [SEER] Program of the National Cancer Institute). Early identification of cases will be accomplished via a rapid reporting system which is already in place within the registry. Controls will be chosen by random digit dialing and will be frequency matched to the cases by age (in five year groups) and race (white, black, other) in a 1:1 control to case ratio. In-person interviews will be conducted by trained interviewers at a time and location of the study subject's choice. An intensive method utilizing expert review of occupational information will be used to ascertain lifelong occupational exposures for each study subject. This approach, developed by Dr. Siemiatycki in Montreal, is based on information supplied by the subject in response to a general occupational questionnaire and detailed questionnaires for specific occupations. The highly industrial setting of the Detroit metropolitan area provides a unique opportunity to explore occupational exposures in substantial detail. In addition to the case control data to be derived from this study, another important product will be the development of a group of professionals in the United States who are skilled in the "technology" of the occupational exposure assessment methods pioneered by Dr. Siemiatycki's group in Montreal.